Inline thermostat control systems and methods

ABSTRACT

A snowmobile coolant system that includes an engine outlet line, an engine inlet line, and an inlet thermostat. The engine outlet line provides coolant flow between an engine and a heat exchanger of the snowmobile. The engine inlet line provides coolant flow between the heat exchanger and the engine. The inlet thermostat is positioned in the engine inlet line and is operable between open and closed states based on a temperature of coolant flowing from the heat exchanger to the inlet thermostat.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of the filing date of U.S.Provisional Application No. 61/565,806, filed Dec. 1, 2011, and entitledINLINE THERMOSTAT CONTROL SYSTEMS AND METHODS, the disclosure of whichis incorporated, in its entirety, by reference.

TECHNICAL FIELD

The present disclosure relates generally to engine coolant systems, andmore specifically relates to snowmobile coolant systems.

BACKGROUND

Many types of engines include a thermostat and an outlet from the engineblock that controls the flow of coolant from the engine block to a heatexchanger (e.g., a radiator) based on a temperature of the coolantexiting the engine block. When the coolant reaches a certaintemperature, the thermostat opens to permit flow of the coolant to theheat exchanger to cool the coolant. The coolant returns to the engineblock at an engine coolant inlet. When the engine is turned off, thecoolant temperature within the engine block tends to spike because thereis no flow of the coolant to the heat exchanger.

Further, the coolant sitting in the heat exchanger may significantlydrop in temperature based on, for example, the ambient environmentalconditions when the engine is restarted within a timeframe when thecoolant within the engine block is still above the operating coolanttemperature and the temperature of the coolant in the heat exchanger isbelow operating temperature, the thermostat remains open and the coldcoolant is moved directly into the engine block. This cold coolant maycause the cylinders of the engine to contract thereby causing frictionand other interference with the pistons. This friction may cause damageto the piston and cylinder. This damage may influence the performance ofthe engine.

SUMMARY

One aspect of the present disclosure relates to a snowmobile coolantsystem that includes an engine outlet line, an engine inlet line, and aninlet thermostat. The engine outlet line provides coolant flow betweenan engine and a heat exchanger of the snowmobile. The engine inlet lineprovides coolant flow between the heat exchanger and the engine. Theinlet thermostat is positioned in the engine inlet line and is operablebetween open and closed states based on a temperature of coolant flowingfrom the heat exchanger to the inlet thermostat.

The snowmobile coolant system may include an outlet thermostatpositioned in the engine outlet line and operable between open andclosed states based on a temperature of coolant flowing from the engineto the outlet thermostat. The snowmobile coolant system may include abypass line providing coolant flow between an outlet of the engine andthe engine inlet line. The bypass line may provide constant flow betweenthe outlet of the engine and the engine inlet line when the engine isrunning. The inlet thermostat may include at least one bleeder hole thatprovides coolant flow through the thermostat when the thermostat is inthe closed state. The inlet thermostat may open and close at atemperature in the range of about 120° F. to about 160° F.

The snowmobile coolant system may include an inlet thermostat housingconfigured to house the inlet thermostat, wherein the inlet thermostathousing includes a housing outlet, a housing inlet, and a side inlet,wherein the side inlet has a smaller cross-sectional size than across-sectional size of the housing inlet. The snowmobile coolant systemmay include a bypass line extending from an outlet of the engine to theside inlet. The inlet thermostat housing may include first and secondhousing pieces, which when assembled together capture the inletthermostat within the inlet thermostat housing.

Another aspect of the present disclosure relates to vehicle dual zonecoolant system that includes first and second thermostats and a bypassline. The first thermostat is positioned in an outlet coolant linecoupled in flow communication between a coolant outlet of an engine anda heat exchanger of the vehicle. The second thermostat is positioned inan inlet coolant line coupled in flow communication between the heatexchanger and a coolant inlet of the engine. The bypass line extendsfrom the engine upstream of the first thermostat to the engine inletline downstream of the second thermostat. The first and secondthermostats may control coolant flow to and from the engine.

The heat exchanger may include a radiator. The vehicle may be asnowmobile and the heat exchanger may be exposed in a drive track tunnelof the snowmobile. The first and second thermostats may be operable toopen and close at a temperature within a range of about 100° F. to about160° F. The inlet thermostat may be carried by a two-part inletthermostat housing. The two-part inlet thermostat housing may include aoutlet, an inlet, and a side inlet, wherein the side inlet is connectedin flow communication with the bypass line.

A further aspect of the present disclosure relates to a method ofcontrolling coolant temperatures in a snowmobile. The method includesproviding an inlet thermostat, an engine inlet coolant line, an engineoutlet coolant line, and a bypass line, connecting the engine inletcoolant line to a heat exchanger outlet and an engine coolant inlet, andconnecting the engine outlet coolant line to a heat exchanger inlet andan engine coolant outlet. The method also includes positioning the inletthermostat in the engine inlet coolant line, coupling the bypass line tothe engine outlet coolant line and the engine inlet coolant linedownstream of the thermostat, and operating the inlet thermostat tocontrol a temperature of coolant entering the engine coolant inlet.

The method may also include providing an outlet thermostat andpositioning the outlet thermostat in the engine outlet coolant line. Theinlet thermostat may include at least one bleeder hole configured toprovide flow through the inlet thermostat when the inlet thermostat isin a closed state. Operating the inlet thermostat may include openingand closing the inlet thermostat based on a temperature of coolantreceived from the heat exchanger.

The foregoing and other features, utilities, and advantages of theinvention will be apparent from the following detailed description ofthe invention with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various embodiments of the presentdisclosure and are a part of the specification. The illustratedembodiments are merely examples of the present disclosure and do notlimit the scope of the invention.

FIG. 1 is a side view of an example snowmobile having a coolant systemin accordance with the present disclosure.

FIG. 2 is a schematic diagram of a coolant system and engine accordingto the prior art.

FIG. 3 is a schematic diagram of an engine and coolant system for avehicle in accordance with the present disclosure.

FIG. 4 is a side view of an example inlet control valve of the coolantsystem of FIG. 3.

Throughout the drawings, identical reference numbers designate similar,but not necessarily identical, elements.

DETAILED DESCRIPTION

One aspect of the present disclosure relates to a coolant system thatincludes multiple thermostats. A first of the thermostats is positionedin a coolant output line extending from the engine block to the heatexchanger. A second of the thermostats is positioned in a coolant inletline that extends from an outlet of the heat exchanger inlet to an inletof the engine block. The first thermostat may control coolant flow tothe heat exchanger by remaining closed until the coolant temperaturewithin the engine block reaches a certain heated temperature (e.g., 125°F.). The second thermostat controls flow of coolant returning to theengine block by remaining closed until the temperature of the coolantreturning from the heat exchanger reaches a certain heated temperature(e.g., 125° F.).

Another aspect of the present disclosure relates to an inlet controlvalve that controls the return flow of coolant to an engine block basedon a temperature of the coolant. The inlet control valve may include thesecond thermostat mentioned above. The inlet control valve may be usedwith a bypass line that extends from a coolant outlet of the engine to aside inlet (also referred to as a bypass inlet) of the inlet controlvalve downstream of the second thermostat. The coolant primarily flowsthrough the bypass line until the temperature of the coolant passingthrough the heat exchanger reaches a certain heated temperature. Theinlet control valve may operate to provide a relatively slow mixing ofthe heated coolant delivered through the bypass line and cooled coolantfrom the heat exchanger at a location downstream of the secondthermostat.

The coolant systems described herein may also be referred to as a dualzone coolant system. The dual zone coolant system may include a firstzone that includes a coolant loop through the first and secondthermostats. A second zone of the coolant system may be defined by thebypass.

In one example, a snowmobile 10 as shown in FIG. 1 includes an engine Aand a coolant system 12. Coolant system 12 may include a heat exchangerC that is exposed within a track tunnel of the snowmobile. The heatexchanger C may be exposed to snow, ice, and ambient air in and aroundthe snowmobile drive track that is significantly lower in temperaturethan a temperature of the engine A.

Referring to FIG. 2, the engine A and coolant system 12 of snowmobile 10are shown schematically for purposes of explaining operation of acoolant system that does not include the inlet control valve or secondthermostat discussed above. When the engine is started cold, the coolantrecirculates within the engine A until the coolant reaches a thresholdtemperature (e.g., in the range of about 120° F. to about 145° F.). Whenthe threshold temperature of the coolant is reached, a thermostat B ofthe coolant system opens to permit coolant to travel through an outletline K to an inlet H of the heat exchanger C. The coolant cools to alower temperature as it passes through the heat exchanger C. The cooledcoolant flows out of an outlet H of the heat exchanger C and through aninlet line L to a coolant bottle or reservoir D. The coolant passesthrough the coolant bottle D and the inlet line L to an inlet O of theengine A. A water pump E may be interposed between the inlet line L andthe inlet O of the engine A.

When the engine A is shut off after running at normal operatingtemperature, the thermostat B remains open because it is exposed tocoolant at or above the threshold temperature (e.g., 125° F.). Becausethe engine is shut off and the coolant is no longer moving, the enginegoes through a heat arc process that can raise the engine temperature toabove 180° F. (e.g., 200° F. or higher). The coolant in the heatedengine may be referred to as super heated coolant. In contrast, thecoolant positioned in the heat exchanger C begins to rapidly coolbecause it may be exposed to, for example, snow, ice and relatively coldambient temperatures where the snowmobile 10 is being used. This cooledcoolant may be referred to as super cooled coolant. The temperature ofthe coolant in the heat exchanger C may drop below 80° F., and sometimeslower than 50° F.

When the engine A is restarted within a time period when the coolantwithin engine A is greater than the threshold temperature to maintainthe thermostat B open, the thermostat B remains open so that cooledcoolant is pushed through the heat exchanger. Typically, coolant in theheat exchanger moves on a first in/first out basis so that the supercooled coolant in the heat exchanger is forced through the inlet line Ldirectly into the engine A. The super cooled coolant, when contactingthe components of the hot engine, tend to cause the engine components(e.g., cylinders) to contract. This contraction may cause additionalinterference and friction of the moving components (e.g., frictionbetween the piston and cylinder) that may cause damage to the enginecomponents. Furthermore, when the super cooled coolant reaches thethermostat B, the super cooled coolant causes the thermostat B to close.When thermostat B closes, the cold coolant is trapped within the hotengine block.

In some examples, the timeframe from starting the hot engine until thecooled coolant is trapped within the engine is less than 10 seconds, andsometimes less than 5 seconds. The change in coolant temperature betweenthe super heated coolant held in the heated engine before starting theengine and the super cooled coolant that becomes trapped in the engineafter starting the engine can be in excess of 100° F., and in some casesgreater than 150° F. This significant change in coolant temperaturewithin the engine in a short period of time may result in the damagediscussed above.

Referring to FIG. 3, an example coolant system 112 in accordance withthe present disclosure may be used with the snowmobile 10. The coolantsystem 112 may control the flow of coolant entering back into the engineA to help avoid the large change in coolant temperature within theengine at the time of restarting a heated engine. Coolant system 112 mayinclude an inlet control valve F and a bypass G. The inlet control valveF is positioned in the inlet line L between the outlet I of the heatexchanger C and the inlet O of the engine A. The bypass G provides abypass of the heat exchanger C by directing at least some coolantexiting an outlet N of engine A to a location downstream of an inletthermostat R of the inlet control valve F. While the schematic drawingof FIG. 3 shows the bypass at a separate outlet N from the outlet M inwhich the thermostat B is connected, other arrangements are possible inwhich the bypass G is connected to the same engine outlet as thethermostat B.

Referring to FIG. 4, an example inlet control valve F is shown ingreater detail. The inlet control valve F includes a side inlet J, firstand second housing members P, Q, an inlet thermostat R, an inlet S, andan outlet P. The inlet thermostat R may be captured within the inletcontrol valve F between the first and second housing members P, Q.Alternative constructions are possible wherein the inlet thermostat R isintegrally formed within the inlet control valve F such as by beingco-molded within a single piece housing of the inlet control valve. Thefirst and second housing members P, Q may be connected in any desiredmanner including, for example, heat welding, sonic welding, laserwelding, adhesives, snap-fit connections, interference fits, brackets,fasteners (e.g., bolts, screws and rivets), and straps. The connectionbetween the first and second housing members P, Q may be permanent ormay provide a releasable attachment.

The inlet thermostat R may include at least one bleeder hole U, V. Thebleeder holes U, V may permit passage of some coolant through the inletthermostat R when inlet thermostat R is closed. The inlet thermostat Rremains closed until coolant being delivered from the heat exchanger Cto the inlet thermostat R reaches a threshold temperature (e.g.,temperatures in the range of about 100° F. to about 160° F., and morepreferably about 130° F. to about 145° F.). In some arrangements, theinlet thermostat R may be rated as a 130° F. thermostat such that theinlet thermostat R opens and closes when exposed to coolant at atemperature of 130° F.

Although two bleeder holes U, V are shown in FIG. 4, inlet thermostat Rmay include any desired number of bleeder holes. The size and number ofbleeder holes may be altered to help the operator control the rate ofcoolant flow through inlet thermostat R when inlet thermostat R is in aclosed state. This rate of flow may determine at least in part an amountof time to mix the super cooled coolant positioned in the heat exchangerwith the super heated coolant delivered through the bypass G from theheated engine A.

The side inlet J is positioned downstream of the inlet control valve Fand connected in flow communication with the bypass G. In somearrangements, the side inlet J is integrally formed with one of thehousing members P, G. In other arrangements, the side inlet ispositioned in the inlet line L at a location separate from the inletcontrol valve F.

The side inlet J may be arranged at an angle of about 30° F. to about60° F., and more preferably in the range of about 40° F. to about 50° F.relative to a length dimension of the inlet control valve F. In oneexample, the inlet diameter of the side inlet J is ⅝ inch and thediameter of a pass-through bore W of the inlet control valve F is about1 inch in diameter. Typically, an inner diameter of inlet thermostat Ris also about 1 inch. The inner diameter of the inlet and outlet linesL, K and the thermostat B may also be about 1 inch, while the bypassinner diameter may be about ⅝ inch. Adjusting the relative sizes betweenthe flow paths of the coolant system 112 may help determine the ratio offlow through the bypass G versus through the inlet thermostat R.

Other arrangements may be made for bleeding predetermined amounts ofcoolant past the inlet thermostat R besides providing bleeder holesthrough the inlet thermostat R. For example, the housing of the inletcontrol valve may include a bypass passage that directs coolant aroundthe inlet thermostat R. In some arrangements, a separate hose or tubemay extend from a position upstream of the inlet thermostat R to aposition downstream of the inlet thermostat R (e.g., a position at theinlet S to a position at the outlet T). The bypass around the inletthermostat R may provide a maximum flow rate that is only a portion ofthe maximum flow rate through inlet thermostat R when inlet thermostat Ris operating into an open position.

A difference in size between the internal diameter of the side inlet Jand the bore W may create a venturi effect within the inlet controlvalve F downstream of the inlet thermostat R. The venturi effect maycreate a vacuum pressure condition at a downstream site of the inletthermostat R that assists in drawing coolant through the bleeder holesU, V. This vacuum condition may assist in accelerating the rate ofcoolant flow through the bleeder holes U, V for a given cross-sectionalsize of the bleeder holes U, V. The increased flow rate resulting fromthe venture effect may permit use of smaller bleeder holes to obtain thesame flow rate as if larger bleeder holes were used without the venturieffect and associated vacuum condition.

In some arrangements, the inlet thermostat R is held by a differentstructure than the inlet control valve F. For example, the inletthermostat R may be held in a chamber or other structure that is part ofthe inlet line L, such as within a hose that defines a portion of theinlet line L. In another example, the inlet thermostat R is held in aportion of the water pump E such as within a housing of the water pump Eor a separate housing or chamber that is attached to the water pump E.The inlet thermostat R may be position in flow communication between thewater pump E and the engine inlet O. Alternatively, the inlet thermostatR may be positioned in flow communication between the outlet I of theheat exchanger C and the water pump E as shown in FIG. 3.

In other arrangements, the inlet thermostat F may be mounted directly tothe engine A (e.g., adjacent to the engine inlet O) or to the heatexchanger C (e.g., adjacent to the outlet I of the heat exchanger C).

Referring again to FIG. 3, when the engine A is started from cold,coolant is recirculated through the engine A and through bypass G andthe inlet line L until the coolant reaches a threshold temperature thatoperates the thermostat B into an open position (e.g., a temperature ofabout 125° F.). Typically, the inlet thermostat R remains closed becausethe coolant flowing from the heat exchanger C to the inlet thermostat Ris below a temperature that would operate the inlet thermostat R into anopen position (e.g., a temperature of about 125° F.). After thethermostat B is opened, the heated coolant from engine A pushes thesuper cooled coolant positioned in the heat exchanger through the inletline L to the inlet thermostat R. This cooled coolant may pass throughbleeder holes U, V to mix with the heated coolant delivered via bypass Gand the side inlet J at a location downstream of the inlet thermostat R.The coolant continues to pass through bleeder holes U, V until thecoolant being delivered from the heat exchanger to inlet thermostat Rreaches an operation temperature that opens inlet thermostat R (e.g., atemperature of about 125° F.).

With both thermostats B, R operating in an open state, the coolantsystem may attain a steady state flow through the outlet line K andbypass G to the inlet line L. In some arrangements, the outlets M, N ofengine A are configured such that about 60% of the coolant flows throughthermostat B and about 40% of the coolant flows through bypass G duringthis steady state condition. Many other ratios are possible for the flowthrough thermostat B and bypass G including, for example, a 50/50 ratio,a 40/60 ratio, and an 80/20 ratio.

When the engine A is shut off after running at normal operatingtemperature, thermostat B and inlet thermostat R remain open. Typically,the engine goes through a heat arc process that can raise the enginetemperature and the associated temperature of the coolant positioned inengine A to above 180° F., and sometimes greater than 200° F. Incontrast, the coolant positioned in heat exchanger C may rapidly cooldue to environmental conditions to which the heat exchanger C is exposed(e.g., snow, ice, and cold ambient temperatures). The temperature of thecoolant in the heat exchanger may drop below 80° F., and sometimes lowerthan 50° F. because no coolant is moving through the heat exchanger C.

Upon restarting the engine within a timeframe in which the temperatureof the coolant within engine A is greater than a threshold temperaturefor maintaining thermostat B in an open state, the super heated coolantfrom engine A is advanced through outlet line K and into heat exchangerC. This flow of heated coolant pushes the super cooled coolant held inheat exchanger C through the coolant bottle D to the inlet thermostat R.The cold temperature of the super cooled coolant operates the inletthermostat into a closed position to prevent the cold coolant frompassing through inlet line L to the engine A. Some of the super cooledcoolant passes through bleeder holes U, V and mixes with the superheated coolant passing through bypass G and side inlet J into the inletline L downstream of the inlet thermostat R.

In some arrangements, a time period in the range of about 30 seconds toabout 3 minutes may elapse during which the super cooled coolant is ableto mix within heat exchanger C and the inlet line L downstream of inletthermostat R (e.g., via mixing provided by bleeder holes U, V) so thatthe coolant temperature delivered to the inlet thermostat R reaches athreshold level that operates the inlet thermostat R into an openposition. This delayed timeframe for mixing of the different temperaturecoolants and exposing the engine block to portions of the super cooledcoolant permit the engine block to adjust without undo constricting thatmay cause damage to the engine A as described above with reference tothe prior art system of FIG. 2.

The examples described with reference to the attached figures relateprimarily to a snowmobile coolant system. However, principles of thecoolant systems disclosed herein may be applicable to other vehicles andengines. For example, the coolant systems disclosed herein, inparticular the use of a thermostat at a coolant inlet of an engine, maybe used with all terrain vehicles (ATVs), motorcycles, utility terrainvehicles (UTVs), watercraft (e.g., boats and personal watercraft (PWC)),automobiles, and engines of every type, size and fuel use.

The preceding description has been presented only to illustrate anddescribe exemplary embodiments of the invention. It is not intended tobe exhaustive or to limit the invention to any precise form disclosed.Many modifications and variations are possible in light of the aboveteaching. It is intended that the scope of the invention be defined bythe following claims.

What is claimed is:
 1. A snowmobile coolant system, comprising: anengine outlet line providing coolant flow between an engine and a heatexchanger of the snowmobile; an engine inlet line providing coolant flowbetween the heat exchanger and the engine; an inlet thermostatpositioned in the engine inlet line and operable between open and closedstates based on a temperature of coolant flowing from the heat exchangerto the inlet thermostat.
 2. The snowmobile coolant system of claim 1,further comprising an outlet thermostat positioned in the engine outletline and operable between open and closed states based on a temperatureof coolant flowing from the engine to the outlet thermostat.
 3. Thesnowmobile coolant system of claim 2, further comprising a bypass lineproviding coolant flow between an outlet of the engine and the engineinlet line.
 4. The snowmobile coolant system of claim 3, wherein thebypass line provides constant flow between the engine outlet and theengine inlet line when the engine is running.
 5. The snowmobile coolantsystem of claim 1, wherein the inlet thermostat includes at least onebleeder hole that provides coolant flow through the thermostat when thethermostat is in the closed state.
 6. The snowmobile coolant system ofclaim 1, wherein the inlet thermostat opens and closes at a temperaturein the range of about 120° F. and 160° F.
 7. The snowmobile coolantsystem of claim 1, further comprising an inlet thermostat housingconfigured to house the inlet thermostat, the inlet thermostat housinghaving a housing outlet, a housing inlet and a side inlet, the sideinlet having a smaller cross-sectional size than a cross-sectional sizeof the housing inlet.
 8. The snowmobile coolant system of claim 7,wherein the inlet thermostat housing comprises two pieces configured toconnect together.
 9. The snowmobile coolant system of claim 7, furthercomprising a bypass line extending from the side inlet to an outlet ofthe engine.
 10. The snowmobile coolant system of claim 7, wherein theinlet thermostat housing comprises first and second housing pieces,which when assembled together capture the inlet thermostat within theinlet thermostat housing.
 11. A vehicle dual zone coolant system,comprising: a first thermostat positioned in an outlet coolant linecoupled in flow communication between a coolant outlet of an engine andan heat exchanger of the vehicle; a second thermostat positioned in aninlet coolant line coupled in flow communication between the heatexchanger and a coolant inlet of the engine; a bypass line extendingfrom the engine upstream of the first thermostat to the inlet coolantline downstream of the second thermostat; wherein the first and secondthermostats control coolant flow to and from the engine.
 12. The vehicledual zone coolant system of claim 11, wherein the heat exchangerincludes a radiator.
 13. The vehicle dual zone coolant system of claim11, wherein the vehicle is a snowmobile and the heat exchanger isexposed in a drive track tunnel of the snowmobile.
 14. The vehicle dualzone coolant system of claim 11, wherein the first and secondthermostats are operable to open and close at a temperature within arange of about 100° F. to about 160° F.
 15. The vehicle dual zonecoolant system of claim 11, wherein the second thermostat is carried bya two-part inlet thermostat housing.
 16. The vehicle dual zone coolantsystem of claim 15, wherein the two-part inlet thermostat housingincludes an engine outlet, a heat exchanger inlet and a side inlet, theside inlet being connected in flow communication with the bypass line.17. A method of controlling coolant temperatures in a snowmobile, themethod comprising: providing an inlet thermostat, an engine inletcoolant line, an engine outlet coolant line, and a bypass line;connecting the engine inlet coolant line to a heat exchanger outlet andan engine coolant inlet; connecting the engine outlet coolant line to aheat exchanger inlet and an engine coolant outlet; positioning the inletthermostat in the engine inlet coolant line; coupling the bypass line tothe engine coolant outlet and the engine inlet coolant line downstreamof the thermostat; operating the inlet thermostat to control atemperature of coolant entering the engine.
 18. The method of claim 17,further comprising providing an outlet thermostat and positioning theoutlet thermostat in the engine outlet coolant line.
 19. The method ofclaim 17, wherein the inlet thermostat includes at least one bleederhole configured to provide flow through the inlet thermostat when theinlet thermostat is in a closed state.
 20. The method of claim 18,wherein operating the inlet thermostat includes opening and closing theinlet thermostat based on a temperature of coolant received from theheat exchanger.